The issue of seawater back-siphoning into the engine
doesn't seem to get talked about a lot, but I've read accounts from some long-distance cruisers that this can be an issue when under sail in rough seas. Although it's likely a pretty rare occurrence, esp. assuming proper siphon loops are in place in both the engine
compartment and at the transom, seawater that is already in the line and/or in the muffler
can apparently make its way back into the engine. Then there's the possibility, of course, of seawater back-siphoning its way in through the transom under following seas. Seems to be more unlikely on the intake side, however, assuming the seacock is closed.
While I've read of various ways to deal with it, one account suggests simply mounting shut-off valves on the discharge side of the mixing elbow
. It would be more accessible (and therefore less likely forgotten) inside the engine compartment (vs. at the transom), and would eliminate the possibility of any water
infiltration that remains in the line and muffler
. The only downside I've uncovered is the prospect of forgetting to open before starting the engine. Even then, however, the engine will apparently just quit, assuming, of course, that you've remembered to open the intake seacock and have therefore avoided impeller damage!
It sounds like a simple solution. I MUST, therefore, be missing something. Any thoughts?